The present invention relates to a method for sensing the status of a waste toner receptacle in a system of an electrophotographic reproduction process and apparatus and, more particularly, to an apparatus and method for sensing whether a waste toner receptacle has been installed in the apparatus and whether the receptacle is full of waste toner.
In general, a system using an electrophotographic process is provided with a container such as a waste toner box for receiving and storing waste toner remaining after the toner formed on a photosensitive drum has been transferred to a printable medium such as a sheet of paper.
As far as a conventional method for sensing whether or not the waste toner box is installed and the waste toner is in a full state is concerted, the amount of the waste toner stored in the waste toner box has been sensed by operation of depressing a sensor due to downward pressure due to the mass of the toner, or by using a photosensor as, for example, shown by the Contamination Sensor by F. B. Abel, U.S. Pat. No. 4,099,861, or the Photoconductive Element Cleaning Apparatus And Residual Toner Collecting Apparatus, by Akira Shimura, U.S. Pat. No. 4,501,484, or the Toner Collecting Apparatus by Tadakazu Ogiri, et al, U.S. Pat. No. 4,730,205. In those prior designs that rely upon mechanical actuation of switches to detect whether the waste toner box is installed as, for example, the movement of a contact lever is sensed by using a contact sensor when the waste toner box is inserted into a system, and to determine whether the waste toner box is full, the need to accommodate the movements of the mechanical components hinders a consumer preference for compactedness in the overall size of the end unit product.
Alternatively, other prior designs rely upon the movement of a lever operating a mechanical actuator to determine whether the waste toner box has been inserted into the developer, and then after the waste toner box is determined to have been installed, light is transmitted from the light emitting unit to the light receiving unit while using the photosensor to detect the condition of waste toner within the receptacle. Such designs rely upon both mechanical and photo-optic sensors, and thus unnecessarily increase the cost of the end unit product, as well as create an additional source of equipment malfunction.
In those designs relying upon photosensors, when light is emitted from a light emitting unit and the waste toner box is not full of waste toner, the light is transmitted to a light receiving unit; if the waste toner box is full however, the light is not transmitted to the light receiving unit. Placement of the photosensors is critical however. In the design of the earlier mentioned Ogiri '205, for example, effort was made to avoid false signals due to scattering of waste toner upon entry into the waste toner box, and the photosensor is located at an uppermost region of the waste toner box while a toner feeding member is rotatably driven along a lower end edge of a toner receiving; port cut into the side of the waste toner box. The design of Ogiri '205 is flawed however, as is noted in the commentary (ostensibly directed however, to Shimura '484) of the Toner Recovery Device by Ryoichi Tsuruoka, in U.S. Pat. No. 4,711,561, because if the power of the toner feeding member introducing waste toner into the side port of the waste toner box is insufficient to push the recovered toner up to the height corresponding to the light path between the photosensors mounted above the waste toner box, "the detection of a toner fill condition will be unreliable.38 Tsuruoka '561 itself however, also uses a side fed waste toner box, but relies upon a vertical fin of a float riding upon waste toner introduced through the side port, to interrupt light transmission along the path, and seems not to address the risk that scattering of waste toner could bury the float within the waste toner box, and thus prevent generation of a toner full signal. Moreover, I have observed that designs following either Ogiri '205 or Tsuruoka '561 essentially equate an unobstructed light transmission path to a normal condition, and make no provision for detecting the absence of the waste toner box, a flaw that absent a mechanically actuated sensor, could result in introduction of waste toner throughout the interior of the end unit product.
Shimura '484 provides in one embodiment, a spring-loaded, light interception plate to block the light transmission path between a light emitting element and a light receiving element while the waste toner container is removed. I have noticed that the photosensor is therefore unable to distinguish between a condition where the waste toner container has not been installed, or has been improperly installed, and a condition where with waste toner container is full of waste toner. In addition to the deficiencies in this design noted in Tsuruoka '561, the light interception plate descends vertically from a horizontally sliding closure member positioned between an auger conveying the waste toner and a top port of the waste toner container. I have also noticed that in designs based upon Shimura '484, either failure of the spring used to position the light interception plate or deposit, whether through scattering or gradual accumulation, of only a small amount of waste toner into the guide channel formed in the bottom of the auger's outer casing for reciprocal movement of the closure member, would hinder correct positioning of the closure member and its vertically descending light interception plate; consequently, either a false indication that the waste toner container is full, a false indication that the waste toner is empty or a false indication of an absent container would be generated, with concomitant undesired effects upon the disposition of the waste toner. Furthermore, beside contributing to unreliability of the finished end unit product and creating a serious risk of malfunction due to introduction of waste toner into the interior of the end unit product during the malfunction, the reliance upon mechanical actuation of the light interception plate contributes to unnecessary cost of manufacture and assembly of the end unit product.
Consequently, in order to avoid the risks noted above, contemporary designs of electrophotographic reproduction systems require that a system be provided with both a photosensor and a mechanical contact sensor for sensing whether a waste toner receptacle is installed and whether or not the waste toner receptacle is in a full state. Accordingly, the cost of each end unit product becomes higher and the structural dimensions of the end unit product become larger due to the space occupied by both photosensor and the mechanical contact sensor.